1. Field of the Invention
This invention relates to a method for continuous roasting of food materials and an apparatus therefor. More particularly, it relates to a novel improvement for the continuous frying, drying and concentration of food materials.
2. Related art
A common method for pan-frying food materials comprises feeding a small amount of oil in a heated pan or frying pan and then heating the food materials together with the oil. When pan-frying, which is one of the easiest cooking operations, is employed at home, a small amount of food materials can be readily fried in a frying pan without requiring much labor or attention. On the other hand, the currently employed methods for cooking a large amount of food materials can be roughly classified into the following three types depending on the shape of the pan and the cooking process.
Namely, xe2x80x9cAtarashii Shokuhin Kako Gijutsu to Sochi (New Techniques and Apparatuses for Processing Foods)xe2x80x9d published by Sangyo Chosa-kai (Jan. 10, 1991) discloses an xe2x80x9cescargotxe2x80x9d type fryer, a xe2x80x9ccupxe2x80x9d type fryer and a fryer provided with an agitator. In the first method of the xe2x80x9cescargotxe2x80x9d type fryer, a pan with a xe2x80x9csnailxe2x80x9d-shaped bottom is slowly rotated horizontally so that food materials are slowly moved toward the outer peripheral of the pan under heating and then once collected therein. Subsequently, the pan is further rotated and inclined at a definite angle. Then the food materials drop into the outer periphery of the pan owing to the gravity of the food materials per se. In this step, the direction of dropping can be altered with the use of small paddles and thus the food materials can be agitated. Also, the food materials drop a specific distance while giving off the excessive vapor therefrom. In this method, the above procedures are carried out repeatedly. In the second method, the xe2x80x9ccupxe2x80x9d type pan is equipped on the inner periphery with one or two plates or projections for carrying up the food materials. Since the cup type fryer normally has no lid, it is somewhat inclined upward in rotational frying. The food materials are slightly carried up from the bottom of the pan by the plate(s) or projection(s) on the inner periphery and turned upside down, thus being agitated. In the method of the fryer provided with an agitator, a pan is not rotated but the food materials are fried with a paddle- or ribbon-type agitator under a planetary motion. Pans of this type are disclosed in, for example, JP-B-57-38255 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) and JP-A-U-62-136193 (the term xe2x80x9cJP-A-Uxe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese utility model applicationxe2x80x9d). In the field of food processing, it has been a practice to roast food materials by using the fluidized gas bed system or the fluidized rotary bed system in the intermediate or final stage of the processing. In the fluidized gas bed system, powdery materials are suspended and fluidized by hot air supplied onto a rectifier such as a porous plate and dried by vigorously mixing with the hot air. In the rotary fluidized bed system, a fluidized bed is divided into small portions by rotating a compartmented rotor and food materials are. fluidized exclusively in each compartment.
The conventional methods for continuous roasting with the constructions as described above suffer from the following problems.
That is to say, in each of the xe2x80x9cescargotxe2x80x9d type fryer, the xe2x80x9ccupxe2x80x9d type fryer and the fryer provided with an agitator, food materials should be replaced each time, which makes the continuous roasting difficult. In these cases, moreover, the qualities of the fried products varies from batch to batch.
In these fryers, furthermore, a large amount of food materials are agitated while being in contact with each other and, therefore, soft materials or softened ones would lose their shapes. In the case of the fluidized gas bed system, continuous roasting can be hardly performed. In addition, it is difficult to suspend and fluidized some food materials in hot air due to the form, size, etc. thereof. On the other hand, food materials in any form can be processed by the rotary fluidized bed system. However, it is needed in this case to employ a complicated and, in its turn, expensive apparatus.
Thus, the present invention aims at providing a less expensive method and apparatus for continuous roasting of food materials whereby the food materials can be continuously roasted regardless of the form thereof and the transfer speed in the cylinder can be continuously and partly changed without losing the shapes of the food materials, thus attaining the optimum roasting and transferring speeds suitable for the conditions of processing the food materials.
The method for continuous roasting of food materials according to the present invention comprises mixing up and transferring a food material in a powdery, particulate, chipped or shredded form in a horizontally placed, tubular cylinder with open ends under heating with the use of a paddle screw provided with a plurality of blades. More particularly, it comprises continuously supplying a food material in a powdery, particulate, chipped or shredded form from an inlet at one end of a horizontally placed, tubular cylinder; then mixing up and transferring said food material in said tubular cylinder with open ends under heating with the use of said paddle screw; and continuously discharging it from an outlet at another end of said tubular cylinder. Furthermore, it comprises supplying the food material quantitatively from the inlet of said tubular cylinder and mixing up and transferring the food material therein in such a state as filling not more than a half of the cross-sectional area of the bore through said tubular cylinder. Furthermore, it comprises mixing up and transferring the food material with a paddle screw provided with angle-adjustable blades.
The apparatus for continuous roasting of food materials according to the present invention comprises: a horizontally placed, tubular cylinder having an open inlet in the rear end side, an open outlet in the front end side, and a bore of a circular cross section formed therethrough; a jacket provided around the outer periphery of said tubular cylinder; a paddle screw rotatably inserted into the bore of said tubular cylinder and consisting of a screw shaft provided with blade(s) via an elastic material; and a rotational drive unit for driving said paddle screw; wherein said blade (s) of said paddle screw are adapted to rotate while being in contact with the inner wall of said tubular cylinder. More particularly, the apparatus is constructed so that a plurality of blades are provided and the inner wall of said tubular cylinder is constructed so that all of the faces thereof are in contact with these blades.
That is to say, in the method and apparatus for continuous roasting of food materials according to the present invention, a food material in a powdery, particulate, chipped or shredded form is supplied from the inlet into the tubular cylinder, heated by the tubular cylinder at a high temperature and successively transferred into the outlet while mixing up with a plurality of angle-adjustable blades adapted to the screw shaft of the rotating paddle screw.
The blades rotate while being in contact with the inner wall of the tubular cylinder. The food material pooled in the lower part of the bore is mixed up by the blades and roasted. The transfer distance can be changed by adjusting the holding angles of the blades. It is possible to adjust the respective holding angles of the blades.
The food material is continuously and quantitatively supplied from the inlet by a supplying unit at a rate appropriate for attaining the desired roasting time or the roasting rate in such a manner as to fill not more than a half of the cross-sectional area of the bore through said tubular cylinder.
Because of filling not more than a half of the cross-sectional area of the bore through said tubular cylinder, a small amount of the food material can be sufficiently mixed up and heated in each bore.
Since the tubular cylinder has the open inlet and outlet, the evaporated components such as vapor formed in the process of frying the food material are discharged therefrom. When a vent port is provided in the middle part of the tubular cylinder, these evaporated components are effectively discharged via this vent port too. If needed, edible oils, water or seasonings may be added via this vent port.
To the food material supplied into the tubular cylinder are added effective amounts of edible oils, water or seasonings at the appropriate point in the course of supplying or frying.
After being supplied into the tubular cylinder, the food material is heated in the optimum state by the heating unit whereby the heating temperature and the transfer speed can be changed along the transfer direction in accordance with the roasting condition.
The blades of the paddle screw are adapted to the screw shaft via the elastic material in such a manner as being in contact with the inner wall of the tubular cylinder. Accordingly, the inner wall comes in contact with the blades at any part. Further, there arises no problem of the unnecessary torque up in the rotational drive unit due to the excessively high extent of contact and the abrasion of the inner wall, blades, etc. is relieved.